Stabilized synthetic lubricant



and!" responding viscosity level.

STABILIZED SYNTHETIC LUBRICANT Alfred H. Matuszak, Westfield, and Ernest V. Wilson,

Roselle, N. J.,assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Application June 25, 1954, Serial No. 439,478

11 Claims. (Cl. 25246.7)

This invention relates to synthetic lubricating compositions. Particularly the invention relates to synthetic lubricating compositions which furnish satisfactory lubricating characteristics at both high and low temperatures.

More particularly, the invention relates to synthetic lubri specific and unusual characteristics made necessary by the technical developments in the last few years, new synthetic lubricants have been developed by the art. One class of materials which has attracted unusual interest as synthetic lubricants are the esters, both the simple esters and the complex type. In general, these synthetic lubricating oils are characterized by lower volatility, higher viscosity indices, and lower pour points than mineral oils of a cor- Lubricants possessing such properties are of special value in the lubricating of moving parts such as combustion turbines, particularly those of the prop jet and turbo-jet type for aircraft. Mineral 'oil lubricants containing added viscosity index improvers,

pour point depressors, or other highly non-volatile additives are undesirable for use in such engines because of their tendency to leave a residue which accumulates and interferes with the operation of the turbine. Yet it has =been found that these additive materials must be added to mineral oils to give them viscosity characteristics essential for operating at the extreme temperature differentials experienced. The synthetic lubricants of the ester type are especially adaptable for use under such conditions since these lubricants have a desirable combination 'of low volatility, low pour points, and high viscosity in New design turbo-jet and turbo prop engines featuring high compression ratios and increased power output have forcedtemperatures upward and have increased the load on gears and bearings. Oil cooling has also become a problem since bearing temperatures in excess of 450 F. are not uncommon. These factors subject the" lubricant to extremely severe conditions with regard to high temperature performance and load handling ability in addition to the ordinary low temperature requirements. Lubricants designed for these engines, therefore, must exhibit an outstanding combination of physical and chemical properties.

As the temperature increases the lubricant tends to thin out or decrease in viscosity. It is essential, however, that at the high'temperature experienced the lubricant retain 2,743,234 Patented Apr. 24, 1956 particularly true for the reduction gear assembly found in the turbo prop engines. Exhaustive tests have shown that the load carrying capacity for a lubricant for this use should be such as to result in a Shell 4-Ball seizure point of about 70 kilograms and a weld point of about 120 kilograms, both values given being minimum values. The explanation of the Shell 4-Ball test is set out in detail below.

In order to prevent excessive oil consumption the lubricant must posses a sufliciently low volatility. The ASTM flash point is used as a measure of volatility and it has been found that lubricants possessing flash points in excess of about 390 F. have been found to be satisfactory in this respect.

The viscosity of the oil at the minimum starting temperature of the engine must be sutficiently low as to prevent serious reduction in the oil flow rate. The maximum viscosity of the oil which can be pumped in adequate quantity has been found to be about 14,500 centistokes at 65 F.

It is generally recognized, therefore, that in order to furnish satisfactory lubrication of the new design turbo jet and turbo prop engines that a lubricant should have a viscosity at 2l0' F. of at least 3.0 centistokes, a viscosity at F. of at least centistokes, a viscosity at 65 F. of no more than 14,500 centistokes, and a load carrying capacity sufficient to'obtain a Shell 4-Ball Extreme Pressure test seizure load of about 70 kilograms and a weld load of kilograms.

It has been found, and forms the object of an application for Letters Patent, Serial Number 316,732, filed October 24, 1952, that blends of diesters and complex esters in conjunction with load carrying additives, exemplified by tricresyl phosphate, are especially adaptable for uses at high and low temperatures where extreme pressure resistance is desired. The instant invention represents an improvement of the blends covered in the above entitled application. i g

It has now'been found that blends of diesters with complex esters as set out in detail in the copending application referred to above can be greatly improved especially in regard to lead corrosivity by incorporating therein a minor amount of practical grade phenothiazine as theoxidation inhibitor which also serves as an effective lead corrosion inhibitor. It has been found, as data set out below will show, that pure phenothiazine is not nearly so adaptable as a lead corrosion inhibitor as is the practical grade phenothiazine. Hence it is desirable, from both the point of view of economics and increased effectiveness to use the commercially available practical phenothiazine as both the oxidation and corrosion inhibitor for the blends to be more completely described below. The practical phenothiazine, which is dark green in color, is the product obtained by heating diphenylamine with sulfur and a trace of iodine catalyst. No purification treatment, other This deposit forms after severaldays storage or after exposure to light, and is believed to be due to the-impurities in the practical grade of phenothiazine. Although the exact composition of the impurities is not known, analysis of this sludge shows that the deposits are the endv products of these impurities and are not found when pure phenothiazine is used as the oxidation inhibitor. It is desirable.- therefore, ..when employing phenothiazine as an oxidation inhibitor in synthetic lubricants 'mary alcohol.

to use the practical grade material in order to 'takeadvantage of its increased corrosion inhibition.

I It is also desirable and equally important to overcome the problem of deposit formation since this sludgy material can lead to oil :fil-ter and oil line plugging, bearing deposits and eventual engine failure. The present invention has as its object the, elimination of this objectionable sludge formation during the'life of the oil.

It-has been found that the'inclusion in thesynthetic lubricant formulation of minor amounts," in the order nf from 0.001% to 5.0% by weight, based on the weight of the finalformulation, of a primary, secondary or .tergtiary amine eliminates the problem of jgdeposit formation. unknown, it is'believed that the amine compoundssolu- ,bilize or neutralize the impurities, thereby preventing their deposition. The samples containing thearnine materials Suitable conditions when employing phos horic acid eat-x alysts of the UOP type are temperatures of 300 F..to. 7 500 -F., pressures frorn'250 to 5,000 p. s. i., andfeed Altho'ngh'the exact rrat-ure'of the phenomenon is remain clear and show no deposit formation after months of storage, even after exposure to light.

Thus, the instant invention has as its object new and useful lubricating compositions which comprise blends of mainly synthetic materials such as diesters ofydibasic acids, complex esters prepared from alcohols, 'dibasic acids and glycols, phenothiazine of a commercial grade, and minor amounts of primary, secondary or tertiary aliphatic amines. r

, A moredetailed description of the component parts of the compositions of invention is set out below.

THE BRANCHED CHAIN 'DIESTER The dibasic acid which is .fully esterii'ied to form the diester portionof the lubricating oil blend may be selected from acids having the formula. HOOC(CH 2)':COOH, a: being 0 to 8. Preferred acids are sebacic, azelaicland adipic acid. 7 These acids are well known in the art and need no further description. v I I f I The branched :chain alcohol which is used to form the which contains from -6 to 16fcarbon atoms in branch chain configuration. It is essential that there be some a degree of branching inthe carbon chain of the alcohol,

and, within limits, the higher the degree of branching the more satisfactory the lubricant. Alcohols such as ethylbutyl, ethylhexyl and other well known branch chain alcohols are operable.

. One group of alcohols that have recently becomecornmercially available and that answer the requirements for the esterifying alcohol are the so-called 0x0 alcohols. These alcohols are preferred and are contemplated in the preferred embodiment of this invention. r

The Oxo alcohols are prepared by thelcatalytic reaction of an olefin with carbon monoxide and hydrogen;

The reaction, 'called Oxo synthesis, occurs at tem peratures in the order of 300-F. to 400 F. at pressures in the range of about 1000 to 3000 p. s. i.: In the diester of the acid is selected from a group of alcohols presence of a suitable catalyst, ordinarily a heavy metal carbonyl, such as cobalt carbonyl, there is formed an aldehyde, which is subsequently hydrogenated to a pripolymers and copolymersof Ca and C4 .monoolefins.

These monoolefins are readily available in refinery streams I and processes for their conversion to 'liquid-copolymers and have been worked out by the art. One such process, known as UOP polymerization, consists of passing the olefin-containing stream in liquid phase in contact with an acid catalyst comprising phosphoric acid impregnated on kieselguhr. Other acidic. catalysts, suchas phosphoric acid or copper phosphate impregnated on silica gel, sulfuric acid, Friedel-Crafts catalysts, activated clays, silicaalumina, copper; pyrophosphatq. etc

fmay be used.

This process is described in U. S. Patent I .No. 2,327,066, issued to Roelen in 1943. I 7 r Itl h as been found that particularly desirable alcohols "(for-the esterification of the'dibasic'acid to prepare the idie'ster component of theblend of this invention maybe prepared by the application of the Oxo synthesis to and mixed butylenes.

'taining propylene and mixed nand isob utylencs;

stocks comprising refinery streams containing propylene Suitable feed stocks, for example, may contain from 15 to mol per cent propylenes, from 0.5 (0.15 mol per cent butylenes, and from 0.1 to 10 mol percent isobutylene, the remaining being saturated hydrocarbons. Other suitable feed stocks are the dimer andtrimerofisobutylene.

Of the Oxo alcohols operable, those alcohols having from 6 to '16 carbon atoms are preferred. .Ihey Ire .pre- 7 paredfrom olefin polymers or copolymershaving from 5 to 15 carbon atoms. In preparing these 'Oxo alcohols,

the desired olefin fraction is segregated from the crude olefin polymer product by fractionation.

As was stated. above, the OXo alcohols are especially desirable esterifying alcohols because of their-optimum degree of branching. For example, the followinguble showsthe structure and percentage composition of a C0 Ox o alcohol prepared from a C1 olefin stream which had been fractionatedfrom the products obtained by the phosphoric acid polymerization of refinery gas stream: con- It will be noted that Oxo alcohols derived from the olefins produced by C3-C4 polymerization are mostly methyl substituted. I I I I Of the preferred Oxo; alcohols operable as the esterifying agent, that is, those 0x0 alcohols having from f 6 to l6 carbon atoms, especially preferred are those alcohols having from 6 to .9 carbon atoms, that is, the 0x0 talcoholsprepared from olefins having'from.-5 to 1 8 carbon atoms; Specifically they arethe Ce Oxoalo'hol;

positions ofthis. inventionis generally known to the art. I

the C7 Qxo alcohol, the Ca Oxo alcohol and the C. 0x0

alcohol. I

v THE COMPLEX ESTER I I I The second componentof'the synthetic lubricating cum as a complei ester. @This, material may be generally described as being the reaction product of two or more of the following compounds; I r r 1. Monohydricalcohols 2. Monob'asic acids 3. Dibasic acids 4. Glycols I 5. Polyhydrichlcohols where at least one polyfunctional alcohol and at least one polyfunctional acid are employed.

These complex esters may be grouped under the following types:

Type I.--Monobasic acid-glycol-dibasic acid-glycol-monobasic acid This complex ester may be considered to have the following structural formula:

wherein R1 and R5 are the alkyl radicals of the monobasic acids; R2 and R4 are the alkyl radicals of the glycols, and

Type lI.-Alch0l-dibasic acid-glycol-dibasic acid-alcohol This ester, especially preferred among all the complex esters, has the following general formula:

R1-0 R2-0oo-Rroo-nr%our 0 0 wherein R1 and R are the combining radicals of the alcohol, R2 and R4 are the alkyl radicals of the dibasic acid,

.and R is the alkyl radical of the glycol.

These esters are prepared as those of Type I above, but preferably they are prepared by first forming the halfester of the dibasic acid and the alcohol, and subsequently reacting two mols of such half-ester with one mol of the glycol.

Type III.Alc0hol-dibasic acid-glycol-monobasic acid This ester may be represented by the following formula:

R1 O RQ%O RFO !CI R4 wherein R1 is the alkyl radical of the alcohol, R2 the alkyl .radical of the dibasic acid, R3 the alkyl radical of the glycol,.and R4 the alkyl radical of the monobasic acid. This ester may be prepared as described in Type I or it 1 may be prepared by reacting a dibasic acid and a glycol under such conditions that one hydroxyl group of the glycol combines with one carboxyl group of the dibasic acid, in other words, so that a half-ester is formed. This half-ester is then reacted with a molar proportion each a of an aliphatic alcohol and a monobasic acid.

' Type IV.M0nobasic acid 'glycol dibasic acid glycol monobasic acid These synthetic complex esters may be said to have the ,general formula:

/ wherein- R1 and R5 are the alkyl radical of the monobasic acid, R2 and R4 are the alkyl radicals of the glycol, and R: is the alkyl radical of the dibasic acid.

,It will be noted that these esters are of the same for- .mula as those appearing above under Type 1, except that this type is prepared by reacting a monobasic acid with a .glycolunder such conditions that a half-ester is formed,

and reacting two mols of such ester with one mol of a f dibasic acid.

The alcohols used in forming the esters set out above include the following: methyl, ethyl, n-butyl, n-hexyl, n-octyl, Z-ethylhexyl, cetyl, oleyl, the ether alcohols formed by the reaction of ethylene oxide or propylene oxide with aliphatic alcohols, etc. One especially suitable group of alcohols are the 0x0 alcohols described in detail above.

in the preparation of the complex esters the following may be listed as illustrative: acetic, propionic, butyric, valeric, capric, caprylic, pelargonic, lauric, palmitic, stearic, oleic, beta-methoxypropionic, beta-ethoxypropionic, beta-tert.-octoxypropionic, beta-ethylmercaptopropionic, beta-tert.-octylmercaptopropionic, beta-ter-t.-dodecylmercaptopropionic acid, and any of the various Oxo acids.

The glycols employed in preparing the complex esters referred to include ethylene glycol and any of the parafiinic homologues of the same containing up to about 18 carbon atoms. These may include, for example, ethylene glycol, propylene glycol, butylene glycol, pinacone, trimethylene glycol, tetramethylene glycol, pentamethylene glycol and the like. Since the glycols may also contain oxygen or sulfur atoms, compounds such as diethylene glycol, triethylene glycol and the polyethylene glycols of the formula:

HO (CH2 CH2O nCHzCHzoH .sebacic acid, and one mol of a glycol such as polyethylene glycol. Specifically preferred is the reaction product according to the above procedure of 2-ethylhexanol, adipic or sebacic acid, and a polyethylene glycol of a molecular weight of about 200.

CORROSION INHIBITOR One important characteristic essential in synthetic lubricants designed to operate at high and low temperatures is that they furnish satisfactory lubricity without undue corrosion of the bearing surfaces they lubricate. In order to enhance these characteristics various additive materials are blended into the finished formulation. Of these materials, one of the most satisfactory in regards the inhibition of lead corrosion is plienothiazine of 'a commercial grade. As was pointed out above, chemically pure phenothiazine is somewhat lacking in its ability to prevent the corrosion of lead and it is difficult to meet existing specifications as to lead corrosivity levels [with pure phenothiazine. It has been found, however, that impure, or commercial grade, phenothiazine, referred to as practical phenothiazine, is quite satisfactory in this respect. it has been found that inclusion in the finished diester-complex ester blend of from about 0.1 to about 2.0 weight percent, based on the weight of the finished composition, of practical or commercial phenothiazine results in a synthetic lubricant that gives very satisfactory lead corrosion results.

With the practical phenothiazine, however, the problem of deposit formation on storage develops. After storage of several days a black sludgy deposit develops which is believed to be due to the impurities present in the practical phenothiazine.

- AMINE I The deposit formation problem occurring with the use of practical phenothiazine is solved according tov the instant invention by inclusion in the formulation of from about 0.001 Wt. percent to about 5.0 Wt. percent, pref wherein R, R and R" are selected from the group consisting of hydrogen and alkyl groups containing from about lie-about '24 carbon atoms. At least one 'alkyl group may contain a functional group selected from NH2,

NI-IR and NR2, although these are not normally required. "The preferred total number of carbon atoms in the amine will depend upon its volatility, solubility and effectiveness 7 omen ADDITIVE MATERIALS.

To enhance other characteristics of the synthetic lubricating compositions of this invention, other additive materials may be blended with the above to obtain a desired finished product. .For example, load carrying properties may be enhanced by including from about 3 to about 10 wt. percent of tricresyl phosphate. Oxidation inhibitors, such as polynuclear phenols, alkylated phenols and the like in amounts varying from about 0.1 to about 2 wt. percent may be used.

Detergent'inhibitors, such as petroleum sul'fonates, or the metal salts such 'as the sodium, zinc, magnesium, barium, ere, salts of petroleum sulfonates in amounts of between about 0.1 and 8 wt. percent may beblended withthe diester-c'ornplex ester blend serving as a base stock. From about 0.1 to about 550 wt. percent of rustinhibitors, such as 'pjo'lyhy'droxy esters, e. 'g., sorbitan 'monooleate, and pentaerythritol monooleate, may be blended into the finished formulation. Lecithin may be 'used in amounts of between about 0.1 and about 2. Wt.

Foam suppressants such as silicone fluids may percent. be added in amounts up to about 0.1 Wt. percent. Mineral oils in amounts of about 5.0 wt. percent to about 15.0 wt. percent or more may be added to aid in rust inhibition.

instant invention.

The invention will be more clearly explained'by reference to the following illustrative examples.

' 7 EXAMPLE I A synthetic lubricant blend was prepared by blending together 95 volume percent of the. cli-Z-ethyl hexanol ester I of sebacic acid'with volume percent of'a complex ester, prepared by reacting two mob of the half ester oil-ethyl hexanol and sebacic acid with one mol of a polyethylene glycol of a molecular weight of about 200. To thisblend was added 3.0 wt. percent of tricresyl phosphateas a load carrying agent. This blend is hereinafter referredto as blend A. V

a. To blend A there was added 1.0 wt. percent of pure phenothia'zine. One portion of this formulation was submitted to a lead corrosion test as follows: Five hundred grams of the test oil was placed in a beaker'equippedwith a stainless steel stirrer 'andan inlet for bubbling air through the oil. the stirrer there were aflixed weighed strips oflead and copper. The oil was heated to a temperature 'of'3'25 F. with stirring'and with air being blown through the sample; This temperaturewas maintained for one hour. .At the conclusion of the test period the lead strip was removed,

cleaned and the loss in weight calculated.

b. The second portion of the formulation was stored portion of this formulation was submitted to the lead corrosion test detailed above and another was stored for 5 months and examined for deposit VEXA'MPLESVIII, IVYAND'V a To samples of blend there was added 1 .0 wt.

V ofpractical phenothiazine and 0.1 wt. percent of di 2 ethylhexyl amine (Example III), 1.0 wt. percept practical phenothiazine and 0.1 wt. percent of his ('di-z-ethylhexyl Various other additive'materials may be blended with the a finished lubricant without departing from the spirit of the On opposite sides of 7 for 5 months-and examinedfor sedimentation and color. 7

EXAMPLE II a. To blend A there was added 1.0 wt. percent ofpractical, or commercially available, phenothiazine.

One

amino) methane, (Example IV) and 1.0 wt. percent practical phenothiazine and 0.1 WL percent of a mixture 7 of Crz-re primary amines ('Example V). These formulations were divided into two portions; one ofwhich'was submitted to the lead corrosion test as set outabove and the other of which was stored for 5 months and examined for sedimentation.

There'sults ofthe experiments performed on the samples as above are setout in theftable below.

Tablel.

Lead Corrosion Months Example Y (mg.w-t., Storage Storage in Light loss) I. Blend n+1.o% Pum so 5 'ssmnie dapultt.

Phenothiazlne. II. Blend A+1:0%,Practtca 5 5 TamPHoavy dark 7 Phenothlazlne. deposit.

Stored in dark.. 5 5' 'Dark, Light de- V a 1 D0 S. 7 III. Blend A+l.0% lrae'tlcal -5' 5 Light amber, No

dfipooitg Phenothlazlne-i-OJfZ, j V di-2-ethylhexyl amine.

IV. Blend A+1.0% Practical 6 5 Phenothlazineal-OdlZ; I V

, amino Methane. T' i V. Blend A+1.0% Practical I 4- 1 6 Phenothiazine+0. 1% I I OrCnPrlmaryAmtne (Primene 811).

nmost No do:

1 L'lqul'dreverts to original darkcolur on shaking but within a tow hours storage repreclpltates the sludge. The blend before storage, however, was dark but perfectly homogeneous. It showedsignsot sludge iormatlon after only several days storage. This increased as storage time continued.

It will be seen that the material of Example III, IV

andV, representing th e'inventive concept, exhibited ex- 'c'ellent lead corrosion resistance in addition to shoviing no sedimentation after 5, months storage. The pure phenothiazine, while giving no deposits, was lacking insetisfactory lead corrosion i resistance.

Stoichiome'tric amounts of diphenyl amine (4b0 parts I by Weight) and sulfur (152 parts by weight) are 'he'a'ted in the presence of 0.3 part "by weight of iodine as a catalyst to a temperature of about 190 to about 200 Gina suitable reaction vessel The heating is continued the evolution-of hydrogen/sulfide ceases, usually for-from V r l to 3 hours. The product .is cooled and removed fran the reaction vessel in thelform of greenish crystals. This e is the practical or impure'grade of phenothiazine referred I to 'hereinbefore. r

In the purification of practical phenothiazin'e, the practical material is dissolved in acetone. After it is completely in solution, the addition of a small amount of water causes precipitation .of the purer materiaL'l If the desired light yellow pro-ductis not-.obtainedbypne; re-

crystallization, the operation may be'repea'ted.

To summarize briefly, this invention'relates to syn 1 thetic lubricating compositions'which comprise blends of from about-2'0 to 95 volume percent of agdiesterof a dibasic' acid containing f-rorn about 5 to about, 15' carbon 1 atoms in th'e ester group with about to about 5 volume percent of a complex ester formed by reacting together at'least three compounds of the' group of Ca ftoCu branched chain alcohols, dib'asic acids, monobasic acids and glycols; To increase the resistance :of the blends-"to lead corrosionthere' is added to them from about 0.1%

to about 2% of a practical grade of phenothiaiine and 'to eliminate deposit formation of the phenothiazine there is added from about QOOl'to about 5.0:wt. percent based Appearance after 7 on the weight of the finished formulation, of an amine selected from the group consisting of primary and secondmy and tertiary aliphatic amines. Other additive materials may also be incorporated into the finished formulation as will be recognized by those familiar with the art.

What is claimed is:

l. A synthetic lubricating oil composition which comprises a blend of from 20% to 95% by volume of a C6 to C16 branched chain alcohol diester of a dibasic acid with from 80% to by volume of a complex ester formed by reacting together at least three compounds of the group of alcohols, monobasic acids, dibasic acids and glycols containing combined therein from 0.1 to 2.0 weight percent, based on the weight of the total composition, of impure phenothiazine which has been prepared by heating stoichiometric amounts of diphenylamine and sulfur to a temperature of about 190 to about 200 C. in the presence of iodine as a catalyst until evolution of hydrogen sulfide ceases, and from 0.001 to 5.0 wt. percent of an amine selected from the group consisting of primary, secondary and tertiary alkyl amines to prevent deposit formation from the commercial phenothiazine.

2. A synthetic lubricating oil composition according to claim 1 wherein said blend comprises 75 volume percent of the diester and 25 volume percent of the complex ester.

3. A composition according to claim 1 wherein said blend comprises 95 volume percent of said diester and 5 volume percent of said complex ester.

4. A synthetic lubricating composition according to claim 1 wherein said branched chain alcohols are the alcohols obtained by subjecting an olefin to the action of carbon monoxide and hydrogen at elevated temperatures and pressures in the presence of a cobalt catalyst.

5. A synthetic lubricating oil composition having a viscosity at 210 F. of at least 3.0 centistokes, a viscosity at 100 F. of at least 11.0 centistokes, and a viscosity at 65 F. of not more than 14,500 centistokes which compn'ses a blend of from 50 volume percent to 95 volume percent of a C6 to C16 branched chain alcohol ester of a dibasic acid selected from the group of adipic, azelaic and sebacic acid with from 50 volume percent to 5 volume percent of a complex ester formed by reacting two mols of a C5 to C16 branched chain alcohol half ester of a dibasic acid selected from the group of azelaic, adipic and sebacic acid with one mol of a polyethylene glycol, said blend containing combined therein from 2% to by weight, based on the weight of the total composition, of tricresyl phosphate, from 0.1 to 2.0 wt. percent of impure grade phenothiazine which has been prepared by heating stoichiometric amounts of diphenylamine and sulfur to a temperature of about 190 to about 200 C. in the presence of iodine as a catalyst until evolution of hydrogen sulfide ceases, and from 0.001 to 5.0 wt. percent of an amine selected from the group of primary and secondary aliphatic amines to prevent deposit formation by the said phenothiazine.

6. A synthetic lubricant according to claim 5 wherein said blend comprises about 75 volume percent of said diester and about volume percent of said complex ester.

7. A synthetic lubricant according to claim 5 wherein said blend comprises about 95 volume percent of said diester and about 5 volume percent of said complex ester.

8. A synthetic lubricant according to claim 5 wherein said branched chain alcohols are obtained by the action of carbon monoxide and hydrogen on an olefin at elevated temperatures and pressures in the presence of a cobalt catalyst.

9. A synthetic lubricant composition which comprises a blend of about volume percent of di-Z-ethylhexyl sebacate with about 25 volume percent of a complex ester prepared by reacting two mols of a C6 to Cis branched chain alcohol half ester of sebacic acid with one mol of a polyethylene glycol having a molecular weight of about 200, said blend containing combined therein from about 0.1 to about 2.0 Weight percent, based on the weight of the total composition, of impure phenothiazine which has been prepared by heating stoichiometric amounts of diphenylamine and sulfur to a temperature of about 190 to about 200 C. in the presence of iodine as a catalyst until evolution of hydrogen sulfide ceases, and about 0.001 to about 5.0 weight percent of an amine selected from the group of primary, secondary and tertiary-alkyl amines to prevent deposit formation from said phenothiazine.

10. A synthetic lubricating composition which comprises a blend of from about 20 volume percent to about volume percent of a diester having the formula ROOC(CH2)xCOOR wherein R and R are branched chain alcohol residues containing from about 6 to about 16 carbon atoms and wherein x is a number of from 2 to 8, with about 80 volume percent to about 5 volume percent of a complex ester of the formula ROOC (CH2 xCOO (CnHZnO yOC(CH2 COOR wherein R and R are branched chain alcohol residues containing from about 5 to about 16 carbon atoms, wherein x is a number of from 2 to 8, wherein n is a number of from 2 to 4, and wherein y is a number of from 1 to 6, said blend containing combined therein from about 0.1 to about 2.0 wt. percent of a commercial grade of phenothiazine which has been prepared by heating stoichiometric amounts of diphenylamine and sulfur to a temperature of about to about 200 C. in the presence of iodine as a catalyst until evolution of hydrogen sulfide ceases and from about 0.001 to about 5.0 Wt. percent of an aliphatic amine, selected from the group of primary, secondary and tertiary amines to prevent deposit formation due to the phenothiazine.

11. A synthetic lubricating composition which comprises a blend of a diester having the formula ROOC (CH2) xCOOR wherein R and R are branched chain alkyl groups containing from about 6 to 16 carbon atoms and wherein x is a number of from 2 to 8 with about 2.0% to 10.0% of tricresyl phosphate, about 0.1 to about 2.0% of a commercial grade of phenothiazine which has been prepared by heating stoichiometric amounts of diphenylamine and sulfur to a temperature of about 190 to about 200 C. in the presence of iodine as a catalyst until evolution of hydrogen sulfide ceases, and from about 0.001% to about 5.0% of an aliphatic amine.

References Cited in the file of this patent UNITED STATES PATENTS 2,190,648 Cantrell Feb. 20, 1940 2,476,271 Bartleson July 19, 1949 2,499,984 Beavers et a1 Mar. 7, 1950 2,639,266 Dilworth et al May 19, 1953 OTHER REFERENCES Aliphatic Esters, Ind. and Eng. Chem., vol. 45, No. 8, pages 1766-1775, pages 1776 and 1767 pertinent. 

1. SYNTHETIC LUBRICATING OIL COMPOSITION WHICH COMPRISES A BLEND OF FROM 20% TO 95% BY VOLUME OF A C6 TO C16 BRANCHED CHAIN ALCOHOL DIESTER OF A DIBASIC ACID WITH FROM 80% TO 5% BY VOLUME OF A COMPLEX ESTER FORMED BY REACTING TOGETHER AT LEAST THREE COMPOUNDS OF THE GROUP OF ALCOHOLS, MONOBASIC ACIDS, DIBASIC ACIDS AND GLYCOLS CONTAINING COMBINED THEREIN FROM 0.1 TO 2.0 WEIGHT PERCENT, BASED ON THE WEIGHT OF THE TOTAL COMPOSITION, OF IMPURE PHENOTHIAZINE WHICH HAS BEEN PREPARED BY HEATING STOICHIOMETRIC AMOUNTS OF DIPHENYLAMINE AND SULFUR TO A TEMPERATURE OF ABOUT 190* TO ABOUT 200* C. IN THE PRESENCE OF IODINE AS A CATALYST UNTIL EVOLUTON OF HYDROGEN SULFIDE CEASES, AND FROM 0.001 TO 5.0 WT. PERCENT OF AN AMINE SELECTED FROM THE GROUP CONSISTING OF PRIMARY, SECONDARY AND TERTIARY ALKYL AMINES TO PREVENT DEPOSIT FORMATION FROM THE COMMERCIAL PHENOTHIAZINE. 